Differences in conditioning using unconditioned stimuli evoking fear, disgust or both emotions simultaneously

Understanding differences in conditioning with stimuli evoking fear and/or disgust is valuable to develop meaningful interventions for phobias, anxiety disorders, and obsessive-compulsive disorders (OCD). We investigated possible differences in the acquisition and extinction of conditioned responses using unconditioned stimuli (UCS) which elicit fear, disgust, or both emotions simultaneously.

Participants underwent a sequential conditioning paradigm over three consecutive days (acquisition, extinction, and extinction retrieval) and were randomly assigned to fear (F), disgust (D), or mixed (FD) conditioning. Pictorial stimuli (UCS) and neutral faces (as conditioned stimuli; CS) were used, with CS-UCS contingency, valence, fear, and disgust ratings as readout measures.

The D and FD groups showed higher valence and disgust ratings after acquisition than the F group, with no group differences in CS-UCS contingency or fear ratings. During extinction, the F group had the greatest reduction in CS-UCS contingency ratings, and the D group showed the largest decrease in disgust ratings for CS+. At extinction retrieval, disgust ratings decreased most in the D group, while fear ratings dropped most in the F and FD groups for CS-. No significant group differences were found for valence during extinction and extinction retrieval.

Conditioning with UCS evoking disgust or disgust and fear simultaneously led to stronger negative valence and disgust responses compared to conditioning with fear-evoking stimuli. Extinction was most effective in the F group (highest reduction of CS-UCS contingency ratings), offering some support for the idea that disgust may be more resistant to extinction than fear.